Biometric technology is discussed in B. Miller, "How to think about identification", The 1995 Advanced Card and Identification Technology Sourcebook, Warfel and Miller Inc., Rockville, Md., 1995.
A state of the art value transfer system is described in U.S. Pat. No. 5,623,547 to Jones et al.
The disclosures of all publications mentioned in the specification and of the publications cited therein are hereby incorporated by reference.